International Concrete Abstracts Portal

SP-162 This fact filled symposium, developed in honor of Mete A Sozen, contains 17 highly informative papers. A spectacular addition to all reference shelves. This symposium took place at the ACI Fall convention in Tarpon Springs, Florida in October of 1994. The Sozen Symposium consisted of three sessions with eighteen speakers. The symposium and this SP volume were organized to permit Mete's students and colleagues to honor and thank him for his council and guidance during their studies at the University of Illinois.

In the earthquake-resistant design of reinforced concrete (RC) buildings, it is necessary to evaluate inelastic behavior and damage of structures both by maximum displacement and by total energy dissipation. In this study, damage assessment of RC structures is carried out based on energy response. Damaging potential of earthquakes to structures is estimated by total input energy; damage of structures is estimated by the damage index taking account of both maximum response and cumulative damage. From the results of parametric inelastic response analyses using simulated earthquakes, it is considered that total input energy depends primarily on earthquake property. The damage parameter proposed by Fajfar, which relates ductility factor to dissipated hysteretic, seems to be relatively stable in many cases. The damage parameter is found useful to represent earthquake response pattern of structures. Using the damage parameter and the damage index, a procedure is presented to find yield force and corresponding ductility factor for given value of damage index. This study shows a possibility of a design concept of RC buildings considering displacement and energy limits.

An evaluation of the implications of the structural system selected for reinforced concrete buildings with three different plan layouts and four different heights (5, 10, 15, and 20 stories) was performed as part of the calibration of the update of the Colombian Seismic Code (10). The buildings had varying amounts of structural walls. In total, 72 buildings were studied. Expected performance of the buildings under the code design earthquake was evaluated using elastic and inelastic procedures. Using the amount of concrete and reinforcing steel for all the buildings and prevalent material and labor prices, a cost of the structure per unit area was determined. Conclusions with respect to behavior and cost implications were obtained for the parameters studied for the different buildings.

Following the strong earthquake in Chile on March 3, 1985, an intensive study was conducted to ascertain why the large inventory of moderate rise buildings in the coastal city of Vina del Mar performed so well during the earthquake. The major findings were that the vast majority of the buildings in this coastal city had a high wall area to total floor area ratio and that the reinforcement detailing in the boundaries of these walls were considerably less than required by U. S. codes. Analytical studies indicated that the high percentage of walls led to significantly lower drifts under severe seismic shaking, thus lowering the ductility demands on the walls. At lower levels of ductility demand, experimental results have demonstrated that wall boundaries did not need special detailing of transverse reinforcement. The findings from the series of research studies following the Chilean earthquake have led to modified U. S. design procedures that relate the need for special detailing in wall boundary elements to expected strain levels along the compression edge of the wall. The expected strain levels are determined based on the aspect ratio of the wall and the percentage of wall area to floor area used in the building.

Force-deformation relationship of high-strength reinforced concrete beam members observed in the laboratory test was idealized by a trilinear relation for use in a nonlinear earthquake response analysis. Methods to evaluate the relationship were examined and the reliability of the methods were discussed with respect to the observed relations. Calculated initial stiffness is shown to significantly underestimate the observed value; a large coefficient of variation was attributed to accidental and shrinkage cracking in the specimen prior to the test. A similar large coefficient of variation was observed in the evaluation of cracking moment. Yield and ultimate moments could be favorably estimated by the theory. An empirical formula was proposed to evaluate yield deformation. An importance of controlling the elastic modulus of concrete in construction is emphasized if a structure is expected to behave as designed during an earthquake.